1. Field of the Invention
This invention relates to power skinning knives for removing the hide of animals during meat processing. More specifically, this invention relates to pneumatically powered skinning knives which use a disc-shaped rotating cutting blade.
2. Description of Related Art
Modern power skinning knives used in meat processing operations are commonly based upon a design in which a pair of disc-shaped toothed blades are driven in opposed cutting oscillations, with the teeth on the blades cutting in scissors fashion. A pair of pushrods mounted on an eccentric shaft drive the blades oppositely. As one blade turns clockwise the other turns counterclockwise until the teeth on one blade pass the teeth on the adjacent blade. The blades then reverse, with the total rotation angle of each blade being only a few degrees. The drive mechanism is operated by a pneumatic motor mounted in the handle of the tool.
This basic configuration has been developed and improved over time resulting in a tool which is reliable, easy to use and easy to maintain. An example of a tool with this general configuration is found in U.S. Pat. No. 5,122,092 issued Jun. 16, 1992. Earlier versions of skinning knives with this counter-oscillating toothed blade design are seen in U.S. Pat. Nos. 4,901,400; 3,739,474; 3,435,522; 4,368,560; 3,176,397; 3,073,027; 2,974,413 and 2,751,680.
An alternative, but less popular, design also uses a pair of toothed blades, however, instead of counter-oscillating, the blades counter-rotate. As the blades move continuously in opposite directions, the teeth repeatedly pass each other, again acting in scissors fashion. This closely related competing design is exemplified in U.S. Pat. Nos. 3,165,833 and 3,277,572.
Importantly, tools with the scissors cutting action have a good cutting "feel" for the operator, allowing him to rapidly guide the tool between the hide and the carcass without damaging either. This "feel" is better than is obtained with the smooth blade of a simple unpowered skinning knife which may inadvertently penetrate the hide or quickly cut too deep, removing valuable meat from the carcass.
Although both of these powered knife configurations are generally successful, they have certain similar problems. The first is that the toothed blades of these designs are relatively difficult to sharpen and expensive to make and replace. The cost and difficulty is compounded by the fact that there are two blades to be sharpened.
A disadvantage in the counter-oscillating design, although that design has proven to be more successful than the counter-rotating design, is that due to the small angle of rotation of the blade, the front of the blade does most of the work. This wears the front of the blade prematurely and requires that the blade be rotated or resharpened frequently.
The counter-oscillating design also has a difficulty in that it induces some vibration into the tool due to the oscillating mass of the pushrods. Although these oscillations can be minimized with careful design, as was done in the design in U.S. Pat. No. 5,122,092, they cannot be completely eliminated.
The present design addresses these problems, and in doing so provides other advantages that are not found in the prior art. Accordingly, it is an object of the present invention to provide a power skinning knife with a blade that distributes its wear uniformly over its cutting edge.
Another object of the invention is to provide a power skinning knife in which the blade can be easily sharpened while it is being used.
Still another object of the invention is to provide a power skinning knife in which the blade is relatively inexpensive to manufacture and to replace.
A further object of the invention is to provide a power skinning knife with a single blade instead of dual blades.
Yet another object of the invention is to provide a power skinning knife with reduced vibration as compared to counter-oscillating designs.
Another object of the invention is to provide a power skinning knife with good cutting feel and cutting depth control to prevent inadvertent deep cuts into the carcass or cuts through the hide.